A number of methods have been employed in the prior art to hermetically seal flexible receptacles such as plastic bags, pouches, and casings. Generally, these methods have been either to heat seal the bag walls together or to apply metal or plastic clips or bands to the gathered and twisted neck of the receptacle or bag. However, while loading a product into a bag the heat seal area may be smeared with grease or otherwise contaminated or the bag walls may have a slight wrinkle or pucker which prevents the formation of a complete, continuous seal. A problem encountered in using clips or bands alone to close a bag is that small, interstitial, air passages or capillary-like voids will be often left open even after the clip or band has been applied under high pressure so that air will eventually leak into or out of the bag. Accordingly, it is one object of the subject invention to present a closure which will positively seal off and close any voids or leaks in the closure and provide a complete, continuous seal for the package.
In order to prevent leakage through gathered folds, preformed caps and caps or closures molded onto the twisted or gathered bag mouths have been used. One such closure is shown in U.S. Pat. No. 3,358,905 which issued on Dec. 19, 1967 to Adrianus Soesbergen wherein a band is placed around the gathered neck of a plastic bag and then a soldering bit is applied to heat melt the twisted end of the bag and close off any discharge passages or interstices which are present in the bag folds. However, if the bag material is a cross-linked or heat set polymer it will not melt and flow according to the Soesbergen patent. Accordingly, it is another object of the present invention to present a method of closing a flexible receptacle which will not be limited to the type of material from which the receptacle is made.
Other prior art closures for flexible receptacles such as bags are disclosed in U.S. Pat. Nos. 3,197,938 and 3,317,119 which issued on Aug. 3, 1965 and May 2, 1967 respectively to Jacob Lasoff.
The foregoing objects are accomplished by the invention which is described in the following paragraph.